The present invention relates to a disk brake which is used for braking a vehicle.
There has been such a disk brake comprising a cast iron caliper consisting of a cylinder portion, a disk-pass portion extending from the cylinder portion so as to cross over a disk, and a pair of pawls which extend from the distal end of the disk-pass portion in a radially inward direction of the disk, the caliper being floatably supported by a carrier which is fixed to the non-rotating section of a vehicle, wherein a pair of pads which are supported by the carrier are pressed against the disk by the relative movement of a piston installed in the bore of the cylinder and the caliper.
In such disk brake, in general, the caliper is integrally cast by using spheroidal graphite cast iron (ductile cast iron). In this case, the ratio of graphite spheroidization and the ratio of formation into ferrite in the metal structure greatly affect the quality (strength). Therefore, the quality has been conventionally ensured by sampling one caliper for each lot or ladle of casting, and by measuring the ratio of graphite spheroidization and the ratio of formation into ferrite by measurement with ultrasonic waves. In ultrasonic wave measurement, as is well known, an ultrasonic wave is input to a sample and the structural condition is determined by the reflectance and transmittance. As a test sample, the caliper must have two substantially parallel flat surfaces (sensor contact surfaces) which serve for attaching probes for transmitting and receiving ultrasonic waves on the caliper.
On the other hand, in the caliper, the surface of various portions are curved to make the unit light. Therefore, the caliper cannot be used as it is for ultrasonic wave measurement. Conventionally, two flat surfaces were cut at appropriate locations on the caliper, for example, in the arm sections, which extend from the cylinder portion in the lateral direction and function as a mount for the caliper, and these flat surfaces were provided as sensor contact surfaces.
If it is attempted, however, to attain a necessary area (about 12 mm.times.12 mm) as a sensor contact surface in the above-noted way, the amount of the material to be cut away becomes significantly large. Therefore, in terms of the strength and the appearance of the caliper, the caliper has to be disposed of as scrap and, as a result, costs are increased.
In this connection, a bore to provide a cylinder portion of the caliper is machined after the casting of the caliper and a plurality of (at least three) reference planes which are later used as the placement reference for machining this bore are integrally formed on the outer surface of the caliper when casting the caliper. The present invention is to take advantage of the reference surfaces for machining the bore. The object of the present invention is to avoid the scrapping of calipers and to reduce production costs by using one of these reference surfaces as a sensor contact surface for ultrasonic wave measurement.